Eighteen dogs underwent 36 femoral artery bypass procedures using autologous femoral vein and, were placed into three groups; no treatment; postoperative treatment with dipyridamole; and postoperative treatment with methylprednisolone. After six weeks, femoral angiography was performed to assess graft patency, the animals were killed, and the grafts removed and prepared for histologic examination. Overall graft patency was 94 percent, with no significant differences among groups. Mean intimal thickness measurements were taken in the proximal, middle, and distal tissues of the grafts to quantitate intimal proliferation. The differences between control and dipyridamole treated groups were not significant. Dogs treated with methylprednisolone had significantly less intimal thickening in the middle third than controls (125 microns vs. 214).